MothBot - a Light Following Robot

Like a Mothbot to a non-flammable torch...or so the saying goes.

Mothbot is a delightfully simple robot which follows a light source.

A perfect robo-pet for young children, the only remote control you need is a torch to lead your Mothbot friend all over the house.

A torch

2 x LDRs

2 x NPN transistors

Battery pack

Breadboard

Jumper wires

2WD Robot chassis with DC motors (like this one https://shop.pimoroni.com/products/mini-3-layer-round-robot-chassis-kit-2wd-with-dc-motors?variant=47037345482)

A moth (3d printed or homemade, your choice)

Mothbot is controlled by two LDRs (Light Dependent Resistors) connected to a pair of transistors which turn the motors on and off. When one of the LDRs detects light, it triggers its transistor to switch on the corresponding motor which turns the robot towards the light.

The circuit diagram is shown above.

The battery pack and circuitry can be hidden on the lower shelf of the chassis, leaving room for the glorious moth above.

It's important that the two LDRs are mounted on the top of the chassis and facing towards the two front corners of the robot. This is what allows Mothbot to steer when it sees light. Test everything out and make sure the circuit is working before inserting jumper cables between the breadboard and the LDRs which can be threaded through the top of the chassis and moved into the final position.

Now it's time to add a beautiful moth to the top.

I used this amazing model from schlossbauer on Thingiverse: https://www.thingiverse.com/thing:4783910

But feel free to create your own moth however you like.

And that's it!

You can now lead your little Mothbot all over the house with nothing but a torch, safe in the knowledge that at least this pet moth will never eat your jumpers.